OSPF routing problem

[katerina.dardoufa]

Dear Community,

In the attached diagram I have include the topology that is giving me a hard time...

Both routers in the top part of the diagram (LANs: 192.168.121.x, 192.168.241-249.x etc) should prefer the route in and out of  ARTEMIS to reach the internal network. MPLS should only be used as a backup.

Traces have proved that incoming traffic from the above networks does go through ARTEMIS. The weird thing is that traffic from the internal network towards 192.168.121.x uses the same route through which it came, but traffic towards 192.168.241-249.x goes through MPLS!!!

Bellow I also include the traces:

------------------------------------------------------------------------

From branches to internal:

traceroute 10.130.201.4 source 192.168.121.1

Type escape sequence to abort.
Tracing the route to 10.130.201.4

  1 192.168.200.6 4 msec 0 msec 4 msec
  2 192.168.200.1 8 msec 8 msec 8 msec
  3 10.130.252.2 8 msec *  8 msec

------------------------------------------------------------------------

traceroute 10.130.201.4 source 192.168.249.1

Type escape sequence to abort.
Tracing the route to 10.130.201.4

  1 192.168.200.1 8 msec 8 msec 8 msec
  2 10.130.252.2 12 msec *  8 msec

------------------------------------------------------------------------

From Internal to branches:

(from lo: 10.130.201.4)

traceroute 192.168.121.1

Type escape sequence to abort.
Tracing the route to 192.168.121.1

  1 10.130.252.1 16 msec 4 msec 0 msec
  2 192.168.200.2 8 msec 8 msec 8 msec
  3 192.168.200.5 8 msec *  8 msec

------------------------------------------------------------------------

traceroute 192.168.249.1

Type escape sequence to abort.
Tracing the route to 192.168.249.1

  1 10.130.254.3 0 msec 0 msec 0 msec
  2 10.130.253.1 0 msec 0 msec 4 msec
  3 10.255.196.82 8 msec 12 msec 12 msec
  4 192.168.200.6 8 msec *  8 msec

------------------------------------------------------------------------

I also include a sh ip route on ARTEMIS

sh ip route 192.168.121.1
Routing entry for 192.168.121.0/24
   Known via "ospf 1", distance 110, metric 18, type intra area
   Last update from 192.168.200.2 on GigabitEthernet0/2, 04:59:30 ago
   Routing Descriptor Blocks:
   * 192.168.200.2, from 192.168.1.121, 04:59:30 ago, via GigabitEthernet0/2
       Route metric is 18, traffic share count is 1

sh ip route 192.168.249.1
Routing entry for 192.168.249.0/24
   Known via "ospf 1", distance 110, metric 2, type intra area
   Last update from 192.168.200.2 on GigabitEthernet0/2, 04:59:35 ago
   Routing Descriptor Blocks:
   * 192.168.200.2, from 192.168.1.240, 04:59:35 ago, via GigabitEthernet0/2
       Route metric is 2, traffic share count is 1

and on 10.130.201.4

sh ip route 192.168.249.1
Routing entry for 192.168.249.0/24
   Known via "ospf 1", distance 110, metric 53, type inter area
   Last update from 10.130.254.3 on Vlan254, 04:04:49 ago
   Routing Descriptor Blocks:
   * 10.130.254.3, from 10.255.198.1, 04:04:49 ago, via Vlan254
       Route metric is 53, traffic share count is 1

sh ip route 192.168.121.1
Routing entry for 192.168.121.0/24
   Known via "ospf 1", distance 110, metric 19, type inter area
   Last update from 10.130.252.1 on Vlan252, 04:04:55 ago
   Routing Descriptor Blocks:
   * 10.130.252.1, from 10.130.201.2, 04:04:55 ago, via Vlan252
       Route metric is 19, traffic share count is 1

As wou can see 10.130.201.4 doesn't learn 192.168.249.x from ARTEMIS but through MPLS!!!!

I should state that on both routers ARTEMIS and APOLLON in the OSPF configuration there is a command:

area 11 range 192.168.240.0 255.255.240.0

Could that be in any way influencing the return of the traffic (lans 192.168.241-249.x) through the MPLS?

Any insight and explaination would be really helpful.

Regards,

Katerina

[katerina.dardoufa]

I also should include : (on ARTEMIS and APOLLON)

sh ip route 192.168.240.0
Routing entry for 192.168.240.0/20, supernet
  Known via "ospf 1", distance 110, metric 2, type intra area
  Routing Descriptor Blocks:
  * directly connected, via Null0
      Route metric is 2, traffic share count is 1

sh ip route 192.168.240.0
Routing entry for 192.168.240.0/20, supernet
  Known via "ospf 1", distance 110, metric 5, type inter area
  Last update from 10.130.253.2 on GigabitEthernet0/3.253, 2d03h ago
  Routing Descriptor Blocks:
  * 10.130.253.2, from 10.130.201.2, 2d03h ago, via GigabitEthernet0/3.253
      Route metric is 5, traffic share count is 1

[Dan-Ciprian Cicioiu]

Hello ,

Could you tell us also the ospf area config of each router

Dan

[katerina.dardoufa]

It seems that the range was the issue!

A collegue beat me to it!!!

I still don't understand why so I will upload the ospf configs

router ospf 1
router-id 192.168.1.121
log-adjacency-changes
network 10.255.196.82 0.0.0.0 area 11
network 192.168.1.121 0.0.0.0 area 11
network 192.168.121.1 0.0.0.0 area 11
network 192.168.200.5 0.0.0.0 area 11

router ospf 1
router-id 192.168.1.240
log-adjacency-changes
network 192.168.1.240 0.0.0.0 area 11
network 192.168.200.2 0.0.0.0 area 11
network 192.168.200.6 0.0.0.0 area 11
network 192.168.241.1 0.0.0.0 area 11
network 192.168.240.0 0.0.15.255 area 11

ARTEMIS

router ospf 1
   router-id 10.130.201.2
   ignore lsa mospf
   log-adjacency-changes
   area 11 range 192.168.240.0 255.255.240.0

  network 192.168.200.1 0.0.0.0 area 11

  network 10.130.201.2 0.0.0.0 area 0
   network 10.130.252.0 0.0.0.3 area 0

etc...

APOLLON

router ospf 1
   router-id 10.130.201.21
   ignore lsa mospf
   log-adjacency-changes
   area 11 range 192.168.240.0 255.255.240.0

  network 10.130.201.1 0.0.0.0 area 0
   network 10.130.253.0 0.0.0.3 area 0

10.130.201.3 & 10.130.201.4 have all interfaces on area 0.

Thanks in advance,

Katerina

[Dan-Ciprian Cicioiu]

I think that the problem was Appolon was receving more specif routes via MPLS.

Artemis was making summary of area 11 ( being ABR ).

Appolon had no connection to area 11, mpls link being area 0 => so you were recevin on the internal equipements the summary inter-area made by Artemis , and the specific routes received by Apolon via MPLS.

switched the names

Dan

[cadet alain]

Hi,

could you also post diagram as jpeg please because not everyone has visio.

Regards.

Alain.

[katerina.dardoufa]

Diagram also in jpg

[Dan-Ciprian Cicioiu · Accepted solution]

Also you can see that Appolon , had the summary made by Artemis , and you should have looked in the routing table for

the specific routes : show ip route 192.168.240.0 255.255.240.0 longer .

sh ip route 192.168.240.0
Routing entry for 192.168.240.0/20, supernet
  Known via "ospf 1", distance 110, metric 5, type inter area
  Last update from 10.130.253.2 on GigabitEthernet0/3.253, 2d03h ago
  Routing Descriptor Blocks:
  * 10.130.253.2, from 10.130.201.2, 2d03h ago, via GigabitEthernet0/3.253
      Route metric is 5, traffic share count is 1

Dan

[katerina.dardoufa]

Dan,

thank you very much for your explanation! It makes sense, since I think that MPLS does have some static routes to 192.168.241-249.x.

I also didn't know the command "show ip route 192.168.240.0 255.255.240.0 longer" which would have been really useful!

Thanks for you help!
Katerina